The Hagen PT565 is the correct replacement media for the following filters:
The PT565 - PowerFlo 1000 - 6 lb. Biological Media is for use with the Laguna Power-Flo 1000 and 4500 filters, and can be used in many underwater and external pond filters. The PowerFlo 1000 filter media features lava rock, which has a large porous surface area and can host large populations of beneficial bacteria. This PowerFlo media will encourage the growth of useful bacteria if placed in the right pond filter media chamber. This aquarium media biologically filters harmful pollutants and toxins, and makes pond water clean and clear.
PT565 - PowerFlo 1000 - 6 lb. Biological Media specifications: